Effectiveness of Maternal mRNA COVID-19 Vaccination During Pregnancy Against COVID-19–Associated Hospitalizations in Infants Aged &lt;6 Months During SARS-CoV-2 Omicron Predominance — 20 States, March 9, 2022–May 31, 2023
Authors: Regina M. Simeone, Laura D. Zambrano, Natasha B. Halasa, Katherine E. Fleming-Dutra, Margaret M. Newhams, Michael J. Wu, Amber O. Orzel-Lockwood, Satoshi Kamidani, Pia S. Pannaraj, Katherine Irby, Aline B. Maddux, Charlotte V. Hobbs, Melissa A. Cameron, Julie A. Boom, Leila C. Sahni, Michele Kong, Ryan A. Nofziger, Jennifer E. Schuster, Hillary Crandall, Janet R. Hume, Mary A. Staat, Elizabeth H. Mack, Tamara T. Bradford, Sabrina M. Heidemann, Emily R. Levy, Shira J. Gertz, Samina S. Bhumbra, Tracie C. Walker, Katherine E. Bline, Kelly N. Michelson, Matt S. Zinter, Heidi R. Flori, Angela P. Campbell, Adrienne G. Randolph, Candice Colston, Heather Kelley, Meghan Murdock, Laura Miron, Ronald C. Sanders, Daniel Hakimi, Jaycee Jumarang, Kennis-Grace Mrotek, Liria Muriscot Niell, Natasha Baig, Lexi Petruccelli, Yamila Sierra, Elizabeth Temte, Imogene Thayer, Frances Zorensky, Nadine Baida, Jong-Ha C. Choi, Caroline R. Ciric, Mark D. Gonzalez, Bria M. Coates, Heather E. Price, Mary Stumpf, Maya Clark, Rylie Dittrich, Suden Kucukak, Eve Listerud, Patrick Moran, Noelle M. Drapeau, Brandi A. Johnson, Lacy Malloch, Lora Martin, Maygan Martin, Kayla Patterson, Cameron Sanders, Shannon Pruitt, Children’s Mercy Kansas City, Melissa Sullivan, Stephanie P. Schwartz, Merry Tomcany, Chelsea C. Rohlfs, Amber Wolfe, Fatima A. Mohammed, J. Nelson Reed, Zachary Rusler, Jack Thomas, Cayla Wakser, Kailee Fernandez, Laura S. Stewart, Leenah Abojaib, Molly J. Kyles
Journal: MMWR Morbidity and Mortality Weekly Report (2023)

Infants aged <6 months are not eligible for COVID-19 vaccination. Vaccination during pregnancy has been associated with protection against infant COVID-19-related hospitalization. The Overcoming COVID-19 Network conducted a case-control study during March 9, 2022-May 31, 2023, to evaluate the effectiveness of maternal receipt of a COVID-19 vaccine dose (vaccine effectiveness [VE]) during pregnancy against COVID-19-related hospitalization in infants aged <6 months and a subset of infants aged <3 months. VE was calculated as (1 - adjusted odds ratio) x 100% among all infants aged <6 months and <3 months. Case-patients (infants hospitalized for COVID-19 outside of birth hospitalization and who had a positive SARS-CoV-2 test result) and control patients (infants hospitalized for COVID-19-like illness with a negative SARS-CoV-2 test result) were compared. Odds ratios were determined using multivariable logistic regression, comparing the odds of receipt of a maternal COVID-19 vaccine dose (completion of a 2-dose vaccination series or a third or higher dose) during pregnancy with maternal nonvaccination between case- and control patients. VE of maternal vaccination during pregnancy against COVID-19-related hospitalization was 35% (95% CI = 15%-51%) among infants aged <6 months and 54% (95% CI = 32%-68%) among infants aged <3 months. Intensive care unit admissions occurred in 23% of all case-patients, and invasive mechanical ventilation was more common among infants of unvaccinated (9%) compared with vaccinated mothers (1%) (p = 0.02). Maternal vaccination during pregnancy provides some protection against COVID-19-related hospitalizations among infants, particularly those aged <3 months. Expectant mothers should remain current with COVID-19 vaccination to protect themselves and their infants from hospitalization and severe outcomes associated with COVID-19.